attributes can be a function

lib/Dancer2/Plugin/JsonApi/Registry/Schema.pm

@@ -90,6 +90,20 @@ Serializes the inner C<$data>.
 
 =cut
 
+has attributes => (
+    is      => 'ro',
+    default => sub {
+        my $self = shift;
+        return sub {
+            my ( $data, $extra_data ) = @_;
+            return {} if ref $data ne 'HASH';
+            my @keys = grep { not $self->relationships->{$_} }
+              grep { $_ ne $self->id } keys %$data;
+            return { $data->%{@keys} };
+        }
+    }
+);
+
 sub serialize_data ( $self, $data, $extra_data = {}, $included = undef ) {
 
     return [ map { $self->serialize_data( $_, $extra_data, $included ) }
@@ -108,12 +122,12 @@ sub serialize_data ( $self, $data, $extra_data = {}, $included = undef ) {
         $s->{links} = gen_links( $self->links, $data, $extra_data );
     }
 
-    $s->{attributes} = +{ pairgrep { $a ne $self->id } %$data };
+    $s->{attributes} = gen_links( $self->attributes, $data, $extra_data );
 
     my %relationships = $self->relationships->%*;
 
     for my $key ( keys %relationships ) {
-        my $attr = delete $s->{attributes}{$key} or next;
+        my $attr = $data->{$key};
 
         my @inc;
 

t/registry-schema.t

@@ -120,6 +120,17 @@ subtest "add the self link if tied to the app" => sub {
     )->serialize(undef);
 
     is $serialized->{links}{self} => '/some/path';
-
 };
+
+subtest 'attributes function' => sub {
+    my $serialized = Dancer2::Plugin::JsonApi::Registry::Schema->new(
+        type       => 'thing',
+        attributes => sub ( $data, @ ) {
+            return +{ reverse %$data },;
+        },
+    )->serialize( { id => 1, 'a' .. 'd' } );
+
+    is $serialized->{data}{attributes} => { 1 => 'id', b => 'a', d => 'c' };
+};
+
 done_testing();